Dimetrodon: Two Measures of Teeth


Dan Raven, Visitor Engagement Volunteer, writes:

My infatuation with the natural world ultimately began with palaeontology. Captivated by worlds and ecosystems as different from those today as ours are from them. Like most children I was fascinated and enamoured with the Mesozoic Era, the age of dinosaurs. However, often neglected, or overlooked entirely, is the Palaeozoic Era, life that preceded the dinosaurs, pterosaurs and mammals among others. One animal that has become symbolic with this era of geological time is a particularly enigmatic predator called Dimetrodon.

My earliest memories of this animal stem back to childhood where I was struck by its bizarre anatomy and the Permian world that it thrived in. There were many extinct and seemingly bizarre animals that captivated me from this young age, however it wasn’t until I became older that I found out about the evolutionary relationships of this animal that it provided me with one of my earliest memories of being awe struck by the natural world.

The resemblances of this animal with that of both extinct and extant (living) reptiles and amphibians, alongside its iconic ‘sail-like’ structure projecting from the spine (the purpose of which has been much debated, but perhaps used for intra-specific display/sexual selection), has led many (initially including myself) to misconstrue this animal’s position in the tree of life. Often portrayed alongside the non-avian dinosaurs within pop culture, the resemblances Dimetrodon shares with any reptile are superficial at best. With traits independently evolving within this animal to that of reptiles e.g the ‘sail-like’ crest, oviparous (egg laying) reproduction and reptile-like teeth, it can be easy to see why many refer to this animal as an obscure reptile.

Commonly referred to as a ‘mammal-like reptile’, this more accurate, although still erroneous term, gives away Dimetrodon’s true evolutionary position. Dimetrodon belongs to a group of vertebrates called the Synapsida, that also includes all of today’s mammals. It shows traits seen in the most basal common ancestors of mammals.  Indeed, the very name Dimetrodon (two measures of teeth) refers to this relationship with mammals, as the presence of different-shaped teeth like this is a common trait in mammals but rare in reptiles.

It is the combination of features in this amazing animal that first inspired me to learn more about natural selection and the evolutionary relationships between animals. It introduced me to the world before the age of dinosaurs and helped foster my passion and interest in natural history, which I hope to share with others with the Museum’s own Dimetrodon and its kin.


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